Not applicable.
(1) Field of the Invention
This invention generally relates to a self adjusting neutral buoyancy countermeasure and system for underwater devices.
More particularly, the invention relates to a self adjusting neutral buoyancy mechanism which effects slight changes in an overall displacement of an underwater body, and thereby adjusts a buoyancy force of the body.
(2) Description of the Prior Art
The current art for devices required to maintain certain depths is known. These include military devices such as torpedo countermeasures and oceanographic survey devices. Acoustic countermeasures are particularly utilized to confuse hostile sonar systems and protect existing force assets. Typical countermeasures are launched from a submarine platform and use an active system to traverse to a predetermined depth, maintain a hovering depth, and begin operation. The known military devices utilize a propeller system or a variable pressure gasbag system to maintain a predetermined depth; however, these systems require active manipulation to maintain their position. In general the devices themselves are slightly negatively buoyant, thus requiring a means of providing additional upward force to maintain depth and prevent the device from free-falling to the ocean bottom.
A propeller system for an acoustic countermeasure device 10 is shown by way of example in FIG. 1. In the case of FIG. 1, constant power is used to maintain the thrust that holds the device 10 at a predetermined depth D. The device 10 is comprised of a body tube 12 which houses power and electronics, a transducer section 14 which produces the acoustic power, and a hovering system 16 which provides thrust and keeps the device at the prescribed depth D in the underwater environment 18. Thus, a problem exists in the art whereby the space and energy requirements for deploying and maintaining depth of one or more underwater devices, such as an acoustic countermeasure device, should be minimized.
This invention describes a countermeasure as a single device and as a system which encompasses the traditional acoustic traits of countermeasures along with a novel hovering system and the use of multiple numbers of these countermeasure devices simultaneously. The invention disclosed here is designed to work on a body that is essentially neutrally buoyant by design, and requires only slight changes to effect depth control. Further, the invention herein utilizes a more passive device for maintaining a predetermined depth which takes less volume, weight and power than traditional methods. The savings in weight, volume and power should allow for a device design that is essentially neutrally buoyant on its own, thus requiring only small changes in buoyancy to effect depth change.
The following patents, for example, disclose various types of depth adjusting devices, but do not disclose a novel hovering mechanism allowing a submerged device to adjust and to maintain a desired depth as does the present invention.
U.S. Pat. No. 2,790,186 to Carapellotti;
U.S. Pat. No. 4,286,539 to Pignone; and
U.S. Pat. No. 4,364,325 to Bowditch.
Specifically, Carapellotti discloses a buoy having an upper enclosed chamber housing a weight therein and a lower chamber joined to the upper chamber. The lower chamber has an open end remote from the upper chamber and a weight therein adapted to pass through the opening. A first removable closure member and a second closure member are provided for the opening, the second closure member being disposed in the lower chamber above the weight. Flexible means connect the weight and the second closure member, and orifices are provided in the lower chamber near the top thereof. When the first closure member is removed from the opening and the buoy is floated, the weight will pass through the opening and be suspended beneath the buoy by the flexible means, the second closure member will lodge on and seal the opening, and the lower chamber will become substantially filled with water.
The patent to Pignone discloses a dual buoyancy device having two external dimensions, in the smaller of which, one end is closed by an elastic sheet undistended, and in the greater of which the sheet is distended from its normal position thereby increasing the external dimension of the device. The distention of the sheet is accomplished by a thruster member bearing on the sheet which thruster is impelled by a weight and lever system actuated by gravity, which causes the thruster to distend the sheet. When the sheet is distended, the overall volume increases causing the device to float. When the sheet is undistended, the overall volume decreases causing the device to sink. Distension of the sheet via the thruster only occurs when the device is inverted. Still further, there is no neutral buoyancy capability. The device either sinks or floats.
Bowditch discloses a passive near neutral buoyancy platform including a structure housing a series of gas-filled cells, restrained in their maximum volume regardless of the internal charge pressure, and collapsible in character when external pressure exceeds the charge pressure. With this structure, once a cell having a predetermined initial internal charge pressure reaches a depth where the external pressure exceeds this initial value, that cell contracts, resulting in a net buoyancy change for the structure. Where this series of cells is attached integrally to a single structure, the cells form a pre-loaded compressibility compensation device matched to the external environment.
It should be understood that the present invention would in fact enhance the functionality of the above patents by providing a displacement mechanism for an underwater body in which the displacement mechanism changes the total displacement of the body and thereby a adjusts a buoyancy force of the body. This is done in the present invention on a substantially neutrally buoyant device and without the use of a known propeller system or a variable pressure gas bag system.
Therefore it is an object of this invention to provide a self adjusting neutral buoyancy device.
Another object of this invention is to provide a self adjusting neutral buoyancy device deployed as a system of devices.
Still another object of this invention is to provide a self adjusting neutral buoyancy device having a mechanism for changing a sealed volume of the device and thereby adjusting a depth at which neutral buoyancy occurs.
A still further object of the invention is to provide a self adjusting neutral buoyancy device which may be incorporated into any underwater neutrally buoyant device.
Yet another object of this invention is to provide a self adjusting neutral buoyancy device which is less costly and requires less space than known devices.
In accordance with one aspect of this invention, there is provided an underwater self adjusting displacement device including a sealed housing having an exterior wall and an inner component area, the exterior wall having an opening formed therein. A sealing plug is slidably seated in the opening of the exterior wall, and an actuator mechanism selectively adjusts the sealing plug within the opening, thereby adjusting a total displacement of the sealed housing. The displacement device is incorporated into any substantially neutrally buoyant underwater deployable device such as an acoustic countermeasure device or an oceanographic sensor device. Further, the deployable devices may be deployed individually or as a field. The displacement device requires less weight and weight within an overall deployed device, enabling large deployments and performance enhancements.